geneticdisorderchromosomalabnormalities.pptx

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1. Genetic Disorders and Chromosomal anomalies Presented by: MARRAH SCS

2. Genetic disorder is a disease that is caused by an abnormality in a n ind i vi d u a l’s D N A. A b no r m a li t ies c a n r a nge from a s ma ll m u t a t i o n in DNA o r a d d i t ion or s u bt r a c t i o n of a n en t ire chromosome or set of chromosomes. Most Genetic disorders are quite rare and affect one person in every several thousands or millions. Genetic disorders may results by Point mutation Deletion of a gene or genes Whole chromosome extra, missing, or both

3. A chromosome anomaly , abnormality or aberration reflects on a typical number of chromosome or a structural abnormality in one or more chromosomes. Chromosome anomalies usually occur when there is an error in cell division following meiosis or mitosis. There are many types of chromosome anomalies. They can be organized into two basic groups, Numerical anomaly Structural anomaly

4. Numerical Anomaly This is called aneuploidy ( an abnormal number of chromosomes), and occurs when an individual is missing either a chromosome from a pair (monosomy) or has more than two chromosomes of a pair . In humans an example of a condition caused by a numerical anomaly is Down Syndrome , also known as Trisomy 21 . An example of monosomy is Turner Syndrome , where the individual is born with only one sex chromosome, an X.

5. Structu r al Anomaly When the chromosome's structure is altered, this can take several forms: Deletion: A portion of the chromosome is missing or deleted. Known disorders in humans include Wolf-Hirschhorn syndrome, which is caused by partial deletion of the short arm of chromosome 4.

6. Duplications: A portion of the chromosome is duplicated, resulting in extra genetic material. Known human disorders include Charcot- Marie-Tooth disease type 1A which may be caused by duplication of the gene encoding peripheral myelin protein 22 (PMP22) on chromosome 17.

7. Translocation: A portion of one chromosome is transferred to another chromosome. There are two main types of translocations: Reciprocal translocation: Segments from two different chromosomes have been exchanged. Robertsonian translocation : An entire chromosome has attached to another at the centromere in humans . T hese only occur with chromosomes 13, 14, 15, 21 and 22.

8. Inversions: A portion of the chromosome has broken off, turned upside down and reattached, therefore the genetic material is inverted and sequence is disturbed.

9. Insertions: A portion of one chromosome has been deleted from its normal place and inserted into another chromosome.

10. Chromosome anomalies can be inherited from a parent . This is why chromosome studies are often performed on parents when a child is found to have an anomaly. If the parents do not possess the abnormality it was not initially inherited ; however it may be transmitted to subsequent generations.

11. 1. Autosomal Disorder   Autosomal Dominant Autosomal Recessive Allosomal Disorder  X- linked dominant  X- linked recessive  Y- linked Mitochondrial Disorder

12. An autosome or somatic chromosomes carry genes which determine the somatic characteristics and do not have any influence on determining the sex of the individual. Autosomes appear in pairs humans have a diploid genome that usually contains 22 pairs of autosomes and one allosome pair (46 chromosomes total). Disorders related to Autosome are autosomal disorders Examples of Autosomal disorder Downs syndrome Haemophilia Sickle cell anemia

13. Autosomal Dominant If the disorder is Autosomal dominant only one infected gene from any one parent is enough to cause the disease in the child. Autosomal Recessive If the disorder is Autosomal recessive there should be transfer of both affected genes from both the parents to cause the disease. If gene from only one parent is transferred then the child becomes a carrier but does not get the disease.

14. Allosomes are sex chromosomes which carry genes responsible for sexual characteristics and as such have a significant role in the determination of sex. Inherited disorders which are related to sex chromosomes are called as Allosomal d i s or d er s Examples of allosomal disorder are Kleinfelder's syndrome Turners syndrome

15. 1. X- linked dominant 2. X- linked recessive 3. Y-linked

16. It is a disorder caused by mutations (or changes) in either mitochondrial DNA or nuclear DNA. If there is mutation in the genes that code for mitochondrial proteins, decreased ATP production leads to energy failure of the cell and eventually, to the organ. These are only passed on from mother since mitochondria is absent in spermatozoa. Frequency: 1 in 4000.

17. A U TOS O M A L DISORDER A L L O S O M AL DISORDER These arise by gene mutation in autosomal chromosomes. These arise by gene mutation in sex chromosomes (mainly X chromosome) They affect the both sexes i.e males and females. They affect more males than females. The mutated gene can be dominant or recessive. The mutated gene is recessive. The suffer is homozygous or heterozygous. Eg Down syndrome, sickle cell anemia. The suffer is hemizygous. Eg Klinefelter syndrome

18. 1. Trisomy 2. Autosomal Deletion 3. Microdeletion 4. Chromosomal Instability

19. T RIS O MY A trisomy is a type of polysomy in which there are three instances of a particular chromosome , instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes) . If the chromosome pairs fail to separate properly during cell division, the egg or sperm may end up with a second copy of one of the chromosomes (non- disjunction). If such a gamete results in fertilization and an embryo, the resulting embryo may also have an entire copy of the extra chromosome.

20. T R IS O M Y The most common types of autosomal trisomy that survive to birth in humans are: Trisomy 21 (Down syndrome) Trisomy 18 (Edwards syndrome) Trisomy 13 (Patau syndrome)

21. TRISOMY 13 (PATAU SYNDROME) Patau Sundrome , also known as Trisomy 13 and Trisomy D. Is a chromosomal abnormality, a syndrome in which a patient had an additional chromosome 13 due to non-disjunction of chromosomes during meiosis. Some are caused by Robertsonian Translocations . The extra chromosome 13 disrupts the normal course of development, causing heart and kidney defects, amongst other features characteristic of Patau syndrome. Patau syndrome affects somewhere between 1 in 10,000 and 1 in 21,700 live births. TR I S O M IC i n t h e c h r o m o s o m e 1 3 . 47 chromosomes

22. FEATURES OF PATAU SYNDROME • • • • • • • Mental deficiency Low birth weight Abnormal development of frontal lobe Absence of corpus callosum Hypoplasia of cerebellum Sloping forehead Scalp defects • • • • • • • Malformed ears Congenital heart defects Renal tract anomalies Microphthalmia Bilateral cleft lip/palate Polydactyly with rudimentary digits Rocker-bottom heel

23. Patau syndrome

24. Patau syndrome

25. Trisomy 18 (Edward Syndrome) • Edward’s Syndrome also kwnon as Trisomy 18 (T18) or Trisome E. • I t is a genetic di s o r der c a u s e d by t h e p r e s e nce of a ll o f a n e x t r a 1 8 t h chromosome (Trisomy 18) due to meiotic nondisjunction. • It is named after John H. Edwards , who first described the syndrome in 1960. It is the second most common autosomal trisomy, after Down Syndrome, that carries to term. • Edward’s Syndrome occurs in around 1 in 6,000 live births and around 80 % of those affected are female.

26. Features of Edward Syndrome • • • • • • Mental deficiency Growth retardation Prominent occiput with elongated head Webbing of the neck Short sternum Micrognathia • • • • • Low-set malformed ears Ventricular septal defects Renal anomalies Clenched fists with overlapping of fingers Hypoplastic nails

27. Edward syndrome

28. Trisomy 21 (Down Syndrome) Down Syndrome also known as Trisomy 21 , is a chromosomal condition caused by the presence of all or part of an extra 21 st chromosome. It is named after John Langdon Down , the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th century by Jean Etienne Dominique Esquirol in 1838 and Edouard Seguin in 1844. Down syndrome was identified as a chromosome 21 Trisomy by Dr. Jerome Lejeune in 1959. The average IQ of children with Down syndrome is around 50, compared to normal children with an IQ of 100. With extra genetic material in chromosome 15. 47 chromosomes

29. Features of Down Syndrome • • Short height Severe mental deficiency with decline in the IQ with age • • • and occiput Flat and low nasal bridge Upward slant to palpebral fissures • • • Brachycephaly with flat face • • • • Malformed large ears Epicanthal folds of the eyes Brushfield spots in iris Renal anomalies Prominent and protruding tongue (scrotal tongue) Simian crease Clinodactyly of 5 th digit

30. Down Syndrome

31. Down syndrome

32. Down syndrome

33. AUTOSOMAL DELETION Autosomal: involves one of the numbered (ie, non-sex chromosomes) Deletion: an abnormality of DNA that involves missing material. These can range from very small (as little as 1 base pair) to very large (involving millions of base pairs of DNA)

34. AUTOSOMAL DELETION  The most common types of autosomal deletion syndromes are: Wolf-Hirschhorn Syndrome Cri Du Chat Langer Giedion Syndrome

35. W o l f - Hi r s c hh o r n Syndrome

36. WOLF-HIRSCHHORN SYNDROME  Wolf-Hirschhorn Syndrome (WHS) , also known as Pitt-Rogers- Danks Syndrome or Pitt Syndrome ----- was first described in 1961 by Americans Herbert L. Cooper and Kurt Hirschhorn and thereafter, gained worldwide attetion by publications by the German Ulrich Wolf and Hirschhorn, Humangenetik a German scientific magazine. DELETION of the short arm of chromosome 4.

37. Wolf-Hirschhorn Syndrome

38. FEATURES OF WOLF-HIRSCHHORN SYNDROME *Short Philtrum *Immunodeficient *Microcephaly (Small Head Size) *Seizures *Muscle Hypotonia *Renal Anomalies *Deafness

39. C r i D u Ch a t

40. CRI DU CHAT CRI DU CHAT also known as chromosome 5p deletion syndrome, 5p minus syndrome or Lejeune’s syndrome. Is a rare genetic disorder due to a missing part of chromosome 5. Its name is a French term (cat-cry or call of the cat) referring to the characteristic cat-like cry of affected children. It was first described by Jerome Lejeune in 1963. The condition affects an 1 in 50,000 live births, strikes all ethnicities, and is more common in females by a 4:3 ratio. DELETION on the short arm of chromosome 5. Cries like a CAT

41. CRI DU CHAT

42. FEATURES OF CRI DU CHAT *Excessive Drooling *Behavioral Problems *Often Mental Retarded *Exhibits Gastorintestinal and Cardiac Complications *Abnormal Development of Larynx and Glottis

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